I realize this is an odd place to put my first post in this subforum, but wanted to chime in on this. Have you cleaned the connection end of the batt? I had one get a little dirty and the post wouldnt pop out like it's supposed to to make contact with the carto. You might try sticking a pin through one of the air holes and prying the post up a bit and then attaching the cart, if that fixes it then the problem is a lack of contact and a good cleaning of your batteries connection terminal, particularly the silicone gasket holding the post, is probably in order and will likely solve the problem.